It would help if you post your groove and characters (and perhaps your brother’s groove) so the advice can be more in depth.
For Sagat:
-Rc’s will definitely discourage him (or anybody who spams predictable moves)
-Well timed jumps and rolls whenever you feel like your brother is going to mash on c.fp. The key is to pay attention to any sort of rhythm or pattern your brother has when he’s attacking and being attacked.
-footsies as the previous poster said… if he uses c.fp for offensive purposes, stay out of the corner and always try to keep the momentum even if it means you have to use an alpha counter once in a while (assuming your groove allows you.)
-if he uses c.fp for defensive purposes-- learn to vary mix-ups (ie. jump-ins, crossovers, rolls, empty jumps, etc.) Players who tend to mash on c.hp usually aren’t well prepared for mix-ups because they lack other moves and occasionally hope that the rocket punch will empty out most of your life-bar.
*remember that c.fp can be stuffed if you’re close enough, but once you get about 2-3 characters away, it usually out prioritizes most moves.
- Mashing on a button ‘hoping’ that it beats c.hp will definitely affect your health… You’ve probably learned the moves that don’t beat c.hp, so try to look up the ones that do.
-If he likes to use c.fp twice in a row up-close: continue to block, jump back, jump up, roll, rc, alpha counter, etc, whenever you feel a second c.fp is coming. Just remember to NOT mash on any button hoping to beat out the second c.hp because it will not work.
-If your brother’s sagat is crouching, expect c.hp. Avoid walking up too close because his finger is hovering over Fierce.
For yama:
-jump/crossover more if your brother does not anti-air consistently. yama does have anti-airs, but several characters out prioritize them or atleast trade for more damage.
-rolling can punish s.hk, but don’t use it too much because he will catch on i suppose.
-staying close will force him to stop using s.hk because it does not have high priority when it’s starting up. if s.hk is your only worry against your brother’s yama then just try to stay up close most of the match.
-as the previous poster said, stay out of the kick’s ideal range. Just like sagat’s c.hp, yama’s s.hk has highest priority once it’s fully extended.
-Just an observation from experience, but i’ve found that a solid air-to-ground offensive is a very effective gameplan. if you jump a little more often, your brother might be more hesitant to use s.hk because he will begin to anticipate a jump… just make sure you don’t make your jumps predictable. Don’t fall into a jumping pattern! 